US Assistant Secretary of State Phil Gordon issued a salutary warning to David Cameron on Wednesday when he stated that a UK withdrawal from the EU would carry negative consequences for the UK's relations with the United States. But the bigger worry for the UK will be when the US decides it is no longer worth commenting about the UK's European future.
Don't bank on US sentimentality
At the height of the debate over the invasion of Iraq, then US Defense Secretary Donald Rumsfeld fired one of his trade-mark verbal flares but this time at the UK's expense. Rumsfeld thought of the UK as part of his 'new Europe' in contrast to France and Germany's ‘old Europe'. But, he noted, if the UK were to decide against committing its military forces to the operation, the US could always 'do a work around'.
While the current US expressions of concern about the UK's growing detachment from Europe need to be taken at face value, Donald Rumsfeld's comment ten years ago should serve as a reminder that the US can also be very unsentimental about its relationship with the UK. US feelings of historical or ideological attachment to Britain can quickly shift into indifference and bloody-mindedness. Past trade disputes with the EU, where UK products have been targeted as a way of encouraging the UK to bring pressure on its EU partners, and the tortuous and decades-long process of securing a bilateral US-UK agreement on defence trade, stand out as telling examples.
The shifting US emphasis from NATO to the EU
During the Cold War, this reality was generally disguised by the shared US and UK insistence on giving primacy to NATO rather than to European integration as the bulwark of security in Europe. After the Cold War, the UK and the US rejected the French view that deeper European political integration was a necessary response to a more multipolar world. The UK was also a leading proponent of the sort of larger but looser EU that US decision-makers supported so ardently.
Today, the US does not fear deeper European integration, even in defence - to the contrary, it would like to see more of both.
In a time of ever-declining European defence budgets, European defence integration is now seen by Mr Gordon and others in the Obama administration as a way of ensuring that European allies retain the capacity to serve as effective military partners to the US.
Moreover, the stability of the eurozone and the success of the structural reforms its members are now undertaking, are an essential component of America's return to sustainable economic growth, given not only the high levels of US merchandise exports to the EU, in the region of $270 billion, but, more significantly, of the sales of US subsidiaries across the EU, estimated at a further $2.5 trillion in 2011.
As a result, the US no longer sees the UK as being helpful when it is an obstacle to deeper European political integration. Ideally, the UK would continue instead to be a voice for open markets within a more integrated EU and a trusted European partner in EU foreign and security policy towards the Middle East and China's rise in East Asia.
Working with, and around, a solitary UK
But the US does not have to rely on an ideal world. If the UK does detach itself, explicitly or implicitly, from the EU, the US can always try another 'work around'. President Obama and senior officials such as Treasury Secretary Tim Geithner have already deepened their channels of communication with Angela Merkel and German politicians, seeing them as the key arbiters of the future of the eurozone which is so important to US economic interests.
And a 'Brexit' would not threaten many aspects of the US-UK special relationship in security. The UK would remain a permanent member of the UN Security Council and a key US military ally in NATO and bilaterally, given its position as one of the world's top military powers with intimate operational and defence industrial linkages with the US. The very close levels of bilateral cooperation on intelligence would also continue, especially given the UK and US's particular interests in the future of Pakistan and Afghanistan and their status as primary targets for Islamist terrorists.
Although it would by no means be its preferred outcome, the US can always overcome the UK's detachment from the EU if it has to. But the UK's political and strategic influence in the US corridors of power would be diminished as a result. Britain would have to fight its corner alone in Washington on trade and regulatory issues. And it would have to guard against becoming or being seen once again as a proxy of the United States on the international stage at a time when the government is trying to chart a more distinctive course for British foreign policy.